1. Field of the Invention
This invention relates to a pictorial communication apparatus for transmitting and receiving a moving or still image and a sound through a communication line.
2. Description of the Prior Art
A pictorial communication apparatus (visual telephone) for transmitting and receiving a moving or still image and a sound through a telephone network is known. FIG. 17 is a block diagram of a prior art pictorial communication apparatus. Numeral 101 is a camera for taking a picture of a user, numeral 102 is a monitor for displaying an image sent from the communication partner or from the camera 101, numeral 103 is a handset having a microphone for receiving a sound and a speaker for outputting a sound. Numeral 104 is a video codec portion for compressing and coding video data obtained from the camera 101 in a predetermined format and expanding and decoding compressed and coded data to display the image on the monitor 102. Numeral 105 is a sound codec portion for compressing and coding a sound signal from the microphone of the handset 103 and expanding and decoding compressed and coded sound data to output a sound from a speaker of the handset 103. Numeral 106 is a multiplex and demultiplex portion for effecting multiplexing, i.e. combining the video data and sound data compressed and coded by the video codec portion 104 and the sound coding portion 105 respectively and for separating a multiplexed signal into the video data and the sound data to supply the video data and the sound data to the video codec portion 104 and the sound codec portion 105 respectively. Numeral 107 is a line interface portion having functions of analyzing a message signal received from the ISDN (Integrated Services Digital Network) 110, judging a kind of a message (such as a setup, a answer, and a disconnection message or the like), judging whether the signal which will be sent is a pictorial communication signal or other signal, and sending a various message on the communication line in addition to the conventional function making connection with the line. Here, the setup message is a message sent from a terminal on a calling side and includes setting information of various calling conditions and a kind of a transmitted signal (such as a pictorial communication signal, a telephone signal or the like). Numeral 108 is a key input portion having a key board and hook key or the like. Numeral 109 is a control portion for effecting a total control for the whole pictorial communication apparatus in response to the inputs form the key input portion 108 for controlling of sending of a answer message from the line interface 107 and an outputting control of a calling bell 111.
FIG. 18 shows a flow chart showing an operation of the prior art pictorial communication apparatus shown in FIG. 17. Hereinbelow an operation of the prior art pictorial communication apparatus shown in FIG. 17 will be described with reference to the flow chart shown in FIG. 18.
At first, the line interface portion 107 detects an arrival of a call by receiving a setup message from the ISDN 110 in step 201. The setup message is analyzed in step 202 and a decision is made as to whether or not the kind of a transmission signal included in the setup message is a pictorial communication signal in step 203 or the message indicates a visual telephone call. If the answer is NO, other processings are executed in step 207. If the answer is YES, that is, it indicates the pictorial communication signal, information of the arrival is sent to the control portion 109. In response to the information of the arrival, the control portion 109 operates the bell 111 to producing a call sound in step 204. Then, when a hook switch becomes in the off-hook condition, the control portion 109 detects the off-hook condition in step 205 and operates the line interface portion 107 to send an answer message. In response to the control portion 109, the line interface portion 107 sends the answer message through the ISDN 110 in step 206. A line interface portion 107 of a pictorial communication apparatus on the calling side received the answer message from the ISDN 110 and analyzes the answer message and confirms a permission message from the called party included in the answer message. This completes the operation of connection between the calling party and called party.
After completion of the connection, communication will start.
Transmitting operation will be described.
A video signal from the camera 101 and a sound signal from the microphone of the handset 103 are compressed and coded by the video codec portion 104 and the sound codec portion 105 respectively. The sound signal and the video signal compressed and coded are multiplexed by the multiplexing and demultiplexing portion 106 to supply a multiplexed signal to the line interface portion 107. The line interface portion transmits the multiplexed signal to the ISDN 110.
Receiving operation will be described.
A transmitted signal (multiplexed signal) through the ISDN 110 is received by the line interface 107 and is supplied to the multiplexing and demultiplexing portion 106. The multiplexing and demultiplexing portion 106 separates the received multiplexed signal into a video signal and a sound signal. These signals are supplied to the video coding portion 104 and the sound codec portion 105 respectively and are subjected to expansion and decoding there. The expanded and decoded video and sound signals are outputted by the monitor 102 and the speaker of the handset 103 respectively.
Another prior art pictorial communication apparatus has a video RAM for storing video and voice messages in addition the structure substantially the same as the first mentioned prior art. When a user is absent, in response of an arrival of a call, it sends the video and sound message to the caller which were recorded previously. After this, it can receive and record an answer message from the caller in the RAM. However, in this prior art pictorial communication apparatus, there is a problem that the cost of the RAM is high.